1. Field of the Invention
The invention relates to a device for pressing an electronic component with different downward forces, and more particularly to the pressing device that is applied to depress an electronic component onto a testing fixture so as to form a combination for testing the electronic component.
2. Description of the Prior Art
Referring to FIG. 1, a schematic view showing a contact of a conventional pressing device and a test socket is demonstrated. As illustrated, the conventional pressing device 1 includes a lift arm 11, a pneumatic damping device 12 and a depressing head 13. The lift arm 11 is to perform the lift operation. The pneumatic damping device 12, a pneumatic cylinder for example, is mainly to apply an exerting force or to act as a buffer for the reaction force. The depressing head 13 is to press down an electronic component C to be tested so as to have accompanying contact points thereof to completely contact corresponding test probes (not shown in the figure) built in the test socket S.
Referring now to FIG. 2A through FIG. 2D, four different stages of a typical depressing stroke of the conventional pressing device of FIG. 1 are schematically shown. In FIG. 2A, the conventional pressing device 1 displaces an electronic component C to an appropriate position over the test socket S. Herein, the pneumatic damping device 12 is preset a predetermined push force for overcoming the required forcing to press down the probes inside the test socket S. Then, in FIG. 2B, the lift arm 11 lowers the depressing head 13 so as to have the electronic component C positioned onto the test socket S.
Further, in FIG. 2C, the lift arm 11 keeps to further lower the depressing head 13, such that the pneumatic damping device 12 would be depressed downward, and then an air-accommodating room As inside the pneumatic damping device 12 would be squeezed so as to generate a downward push forcing upon the electronic component C. Thus, sufficient forcing would be finally obtained to overcome the aforesaid required forcing for ensuring fully contact between the contact points of the electronic component C and the probes in the test socket. At this time, in FIG. 2D, a testing upon the electronic component C can be started.
Referring now to FIG. 3, a plot demonstrating a pressure change of the conventional depressing head upon the electronic component is shown. Namely, during the stroke of depressing the electronic component C onto the test socket S as shown in FIG. 2B and FIG. 2C, i.e. upon when the electronic component C is placed on the test socket S and the lift arm 11 is lowered to perform the contact push, then a severe-fluctuated forcing waveform would be abruptly generated to the downward pressure. As shown in FIG. 3, the severe-fluctuated forcing waveform is demonstrated bun the spikes from point B to point D. However, to a fragile chip (a glass-based chip for example), such a fluctuation in the downward pressure would imply a risk to break or fracture the chip.
Refer now to FIG. 4A through FIG. 4C; where FIG. 4A is a plot demonstrating a contact-pressure change of the depressing head while the downward pressure is set to be 1 kgf, FIG. 4B is a plot demonstrating a contact-pressure change of the depressing head while the downward pressure is set to be 3 kgf, and FIG. 4C is a plot demonstrating a contact-pressure change of the depressing head while the downward pressure is set to be 5 kgf. As shown in FIG. 4A, by having a typical test on the conventional equipment for example, in the case that the downward pressure is preset to be 1 kgf, then the highest peak of the fluctuated downward pressure would reach 1.9 kgf, and the fluctuating duration would be about 0.022 seconds. Further, as shown in FIG. 4B, in the case that the downward pressure is preset to be 3 kgf, then the highest peak of the fluctuated downward pressure would reach 7 kgf, and the fluctuating duration would be about 0.031 seconds. In addition, as shown in FIG. 4C, in the case that the downward pressure is preset to be 5 kgf, then the highest peak of the fluctuated downward pressure would reach 8.8 kgf, and the fluctuating duration would be about 0.035 seconds.
As described above, from FIG. 4A to FIG. 4C and also by the aforesaid explanation, the highest peak at the fluctuated downward is pressure would reach almost twice of the preset value. Such an instant high downward pressure would be definitely a difficulty to the high-precision chip. It can be foreseen that a broken chip might be inevitable. Further, it shall be particularly cautious that potential cracks out of visions of naked eyes might exist on this chip. It is quite possible that, after some service hours, these potential cracks might grow to a degree that a normal operation of the chip would be infeasible. Thereupon, efficiency and service life of the chip would be significantly reduced.